The present invention relates to a controller that controls the rotational speed of a brushless motor to achieve a desired motor speed; and, more particularly, the invention relates to an air conditioner that conditions interior air by controlling the brushless motor driving its internal compressor/blower using this controller, to a refrigerator that provides refrigeration by controlling the brushless motor during its internal compressor/blower using the controller, to a washing machine that washes clothes by controlling the brushless motor during its pulsator or spin-basket using the controller, and to a vacuum cleaner that cleans rooms by controlling the brushless motor driving its blower using the controller.
Because of their easy maintenance, brushless motors, which include a combination of a permanent magnet rotor and stator coils, are used in air conditioners, refrigerators, washing machines, and the like.
Brushless motor driving control requires close linking between the magnetic pole position of the rotor and the positions of the stator coils. A sensorless position detection scheme utilizing the counter-electromotive force induced into the stator coils by their interactions with the magnetic pole of the rotor is employed to detect the magnetic pole position of the rotor; it is not detected using a rotor position detection sensor, such as a Hall element.
Brushless motor drives using the sensorless position detection scheme include those set forth in, for example, Japanese Application Patent Laid-Open Publication No. Hei-6-284783 and Hei-6-98583. For these brushless motor drives, which are so designed as to detect the crossing point (namely, the rising or falling edge) between the terminal voltages of the motor and a reference voltage, the required electrical angle (for example, 15 degrees) is calculated in one way or another immediately after commutation so that a spike voltage signal will not be detected as a rotor position detection signal, and the time corresponding to this electrical angle is set as a position detection inhibition interval. During this inhibition interval, signal detection is inhibited, and signals are acquired only after the elapse of the inhibition time. Or, the crossing point (namely, the rising or falling edge) with respect to the reference voltage is detected by modifying the pattern of chopping by only the upper and lower switching devices among all six switching devices, and motor control is based on the detection position.
For conventional brushless motor drives, since the required electrical angle must be calculated in one way or another immediately after commutation, the use of a microcomputer or the like to calculate this angle increases the processing time required, or the use of an external circuit to perform the calculation requires a complex circuit composition.
In the case of these conventional brushless motor drives, although mis-judgment based on the spike voltage developed during the inhibition interval can be prevented by providing the inhibition interval, if an abrupt load change causes output of a rotor position detection signal during the inhibition interval immediately after commutation, this signal cannot be detected. For this reason, there arises a problem in that, since a position significantly offset from the actual position of the rotor is likely to be mis-judged as the actual rotor position, the operation becomes unstable or the motor decreases in operational efficiency or steps out.
An object of the present invention is to provide a brushless motor controller that can properly detect the position of a rotor immediately after commutation, without being provided with a position detection inhibition interval immediately after commutation.
Another object of the present invention is to provide a low-cost and simplified brushless motor controller that is high in rotor magnetic pole position detection accuracy and is capable of accurately controlling the corresponding brushless motor as well.
Still another object of the present invention is to provide a motor controller that can properly control a brushless motor without stopping it, even during a very long interval of flow of a reflux current after power-on switching.
A further object of the present invention is to minimize position detection errors due to noise.
A further object of the present invention is to provide a brushless motor controller that can minimize the occurrence of a power-on malfunction due to noise.
A further object of the present invention is to provide a brushless motor controller that can automatically attach importance to more efficient or faster operation during brushless motor operational control.
A further object of the present invention is to provide a brushless motor controller that covers a larger control range.
A further object of the present invention is to provide appliances, especially an air conditioner, a refrigerator, a washing machine, and a vacuum cleaner, that are powered from the brushless motor thus controlled.
A feature of the present invention for achieving the objects described above is characterized in the fact that a first information signal pattern is stored into an information signal pattern storage means; and, when the first information signal pattern and a third information signal pattern are the same and a second information signal pattern is different from the other two patterns, a reflux current decay signal is generated by an information signal pattern comparison means.
According to this feature, when the first information signal pattern and the third information signal pattern are the same and the second information signal pattern is different from the other two patterns, since a reflux current is generated immediately after commutation and is then decayed, the information signal pattern comparison means compares the first information signal pattern, the second information signal pattern, and the third information signal pattern, and generates a reflux current decay signal. Thus, the loss of the reflux current can be detected. As a result, the position of the rotor can be properly detected immediately after commutation, without providing a rotor position detection inhibition interval, by detecting the loss of the reflux current and then detecting the rotating position of the rotor in accordance with the information signal patterns created by the corresponding information signal generation means. Even if the load changes abruptly, the corresponding brushless motor can also be driven with rapid response, since no inhibition time interval needs to be calculated.
In addition, since rotor position detection is possible without the chopping pattern of any switching device, the position of the rotor can be detected properly, even if the upper or lower three of six switching devices low operating speed devices and are inexpensive.
Another feature of the present invention resides in the fact that the first information signal pattern that has been stored into the above-mentioned information signal pattern storage means is changed to the second information signal pattern by an information signal pattern changing means using a reflux signal decay signal.
According to this feature, when the first information signal pattern and the third information signal pattern are the same, and the second information signal pattern is different from the other two patterns, since a reflux current is generated immediately after commutation and is then decayed, and since the second information signal pattern is an information signal pattern corresponding to the rotor position to be detected, the position of the rotor can be properly detected immediately after commutation, without providing a rotor position detection inhibition interval, by detecting from all information signal patterns generated by the information signal generation means, only the information signal pattern matching the second information signal pattern stored within the information signal pattern storage means, and then detecting the rotating position of the rotor in accordance with that detected information signal pattern.
Still another feature of the present invention resides in the fact that, when the fourth information signal pattern matches either of the information signal patterns stored within the information signal pattern storage means, an information signal pattern match signal is generated by the information signal pattern comparison means and the rotating position of the rotor is detected by a rotating position detection means using the information signal pattern match signal.
According to this feature, when detection of the loss of the reflux current is followed by matching between the fourth information signal pattern and either of the information signal patterns stored within the information signal pattern storage means, since the fourth information signal pattern is an information signal pattern corresponding to the rotor position to be detected, the information signal pattern comparison means compares the fourth information signal pattern and all other information signal patterns stored within the information signal pattern storage means and generates an information signal pattern match signal. Thereby, the rotating position detection means can properly detect the position of the rotor immediately after commutation, without providing a rotor position detection inhibition interval, by detecting the rotating position of the rotor in accordance with the information signal pattern match signal and the corresponding information signal pattern generated by the information signal generation means.
Still another feature of the present invention resides in the fact that, when the required time has elapsed from commutation, the first information signal pattern that was stored into the information signal pattern storage means is changed to the second information signal pattern by the information signal pattern changing means.
According to this feature, even if the reflux current interval that follows power-on switching is too long for the loss of the reflux current to be detected, the magnetic pole position of the rotor can be detected and the motor can be properly controlled at a low cost.
A feature of the present invention is characterized in the fact that, for a brushless motor controller that detects the magnetic pole position of the stator from the terminal voltages of the stator coils of each phase and controls the energization (power-on) of these stator coils, the position of the rotor can be detected immediately after commutation, by entering directly into the control circuits of the controller a comparison result information signal, which is obtained through comparison between the detected voltages corresponding to the above-mentioned terminal voltages, and a reference voltage.
Another feature of the present invention is characterized in the fact that the position of the rotor can be detected without using the chopping pattern of any switching device.
Still another feature of the present invention is characterized in the fact that the comparison result information signal, which is obtained through comparison between the detected voltages, corresponding to the above-mentioned terminal voltages, and a reference voltage, is directly entered into the control circuits, the PWM signal on/off interval is judged in the control circuits, and the delay time for both the PWM signal received from the control circuits and the PWM signal applied to the motor can be set using either an updatable EEPROM, a variable resistor, or the like.
A further feature of the present invention is characterized in the fact that the position of the rotor is detected from the comparison result information signal pattern corresponding to the terminal voltages of the stator coils of multiple phases.
A further feature of the present invention is characterized in the fact that the power-on pattern for the stator coils is determined from the comparison result information signal pattern corresponding to the terminal voltages of the stator coils of multiple phases.
A further feature of the present invention is characterized in the fact that the interval during which a reflux current flows following power-on switching is detected from the comparison result information signal pattern corresponding to the terminal voltages of the stator coils of multiple phases.
A further feature of the present invention is characterized in the fact that the phase signal pattern to be checked for position detection is updated after the reflux current developed through power-on-switching has been lost.
A further feature of the present invention is characterized in the fact that when the required time elapses from power-on switching, even if the reflux current interval is very long, the next power-on switching can be executed by updating forcibly the signal pattern checked.
A further feature of the present invention is characterized, in the fact that power-on phase selection is based on either comparison result information, the received phase control command from an external circuit, the contents of the EEPROM, the rotational speed of the motor, or the calculated electrical quantity corresponding to the amount of current flowing into the inverter or motor.
A further feature of the present invention is characterized in the fact that, in a PWM control region, importance is attached to operational efficiency during phase control, and in a high-speed rotation control region, control is provided to advance the power-on phase.
A further feature of the present invention is characterized in the fact that, even if the three upper or lower of all six switching devices are low in operating speed and inexpensive, the position of the rotor can be detected properly.
A further feature of the present invention is characterized in the fact that a simple position detection software configuration can be included in the control circuits.
A further feature of the present invention is characterized in the fact that the size of the data table within the internal position detection software of the control circuits and the occupancy of a RAM or ROM can be minimized.
And, a further feature of the present invention is characterized in the fact that the brushless motor controlled by such controller as described above can be used as the power supply for an air conditioner, a refrigerator, a washing machine, or a vacuum cleaner.